This invention relates to electronic devices, and more particularly, to illuminating a keypad of an electronic device and detecting operation of a key on the keypad by the user of the electronic device.
It is known to mount light-emitting diodes (xe2x80x9cLEDsxe2x80x9d) and switches directly on a main printed circuitboard (xe2x80x9cPCBxe2x80x9d) or a dedicated PCB for use with the keypad of an electronic device. Light from the LEDs is diffused by a translucent light guide overlaying the LEDs, thereby illuminating the keypad.
One problem associated with the above-described construction is that it may complicate the design of complex PCBs, which must meet continuing demands for increased circuit density and reduction in the overall product size/volume for electronic devices. More specifically, keypads and their supporting components, such as LEDs and switches, tend to take a large amount of PCB area for implementation, thereby reducing the area available for other circuits and/or components on the PCB. Furthermore, to accommodate other electronic components and circuits in the keypad area overlying the PCB, holes may have to be cut in the light guide and/or the locations of the LEDs may have to be compromised, thereby potentially reducing the quality of keypad illumination (i.e., low light levels and uneven illumination).
In accordance with the present invention, an electrical assembly is provided for use with a keypad for an electronic device including at least one plunger associated with a key, the plunger being moveable between a first position and a second position relative to the electrical assembly in response to operation of the key by a user.
In one form, the electrical assembly includes a light guide, and at least one electrical component carried by the light guide and positioned to underlie the key for at least one of a) illuminating the key, and b) changing between a first electrical state and a second electrical state in response to the plunger moving between the first and second positions to indicate that the key has been operated by a user.
In one form, the light guide has a first surface defining a keysite positioned to underlie the key, and the at least one electrical component includes at least one light source carried in the light guide underlying the keysite to direct light through the keysite to illuminate the key.
In one form, the at least one electrical component includes an open electrical circuit defined by a conductive grid. The circuit is closed by contact with a conductor grid on the plunger with the plunger in one of the first and second positions.
In one form, the light guide has a first surface defining a keysite positioned to underlie the key, the conductive grid is mounted on the first surface at the keysite, and the at least one electrical component further includes at least one light source carried in the light guide beneath the keysite to direct light through the keysite and the conductive grid to illuminate the key.
In one form, the electrical assembly further includes a bus carried by the light guide for electrically connecting the circuit and the light source to at least one other component of the electronic device.
In one form, the electrical component is embedded in the light guide.
In one form, the electrical assembly includes a light guide, and a switch carried by the light guide. The switch is configured to change between a first electrical state and a second electrical state in response to the plunger moving between the first and second position to indicate that the key has been operated by a user.
In one form, the electrical assembly further includes a light source carried by the light guide for illuminating at least a portion of the key pad.
In one form, the electrical assembly further includes a bus carried by the light guide for electrically connecting the switch and the light source to at least one other component of the electronic device.
In one form, the switch is embedded in the light guide.
In one form, the switch includes a light source and an optical detector. The light source and the optical detector are positioned by the light guide so that movement of the plunger between the first and second positions interrupts a light signal transmitted to the optical detector from the light source.
In one form, the switch includes a light source and an optical detector. The light source and the optical detector are located in the light guide so that movement of the plunger between the first and second positions causes a light signal from the light source to be directed to the optical detector.
In one form, the switch includes a magnetic switch that is responsive to a changing magnetic field produced by movement of the plunger between the first and second positions.
In one form, the switch includes a conductive grid on the light guide that is contacted by a conductor on the plunger with the plunger in one of the first and second positions.
In accordance with one aspect of the invention, a method is provided for illuminating a keypad of an electronic device and detecting operation of a key on the keypad by a user. The method includes the steps of generating light in the electronic device, transmitting the light to the keypad through a light guide to illuminate at least part of the keypad, and generating a changed electrical state for the electronic device from a location in the light guide in response to operation of the key by a user.
In one form, the step of generating a changed electrical state includes the step of altering a light signal in the light guide to change the electrical state for the electronic device.
In one form, the step of generating a changed electrical state includes the step of altering an electromagnetic field in the light guide to change the electrical state for the electronic device.
In one form, the step of generating light in the electronic device includes the step of generating the light from a location in the light guide.
In one form, the step of transmitting light includes the step of transmitting the light from a location in the light guide to the at least part of the keypad.
In accordance with one aspect of the invention, a method is provided for illuminating a key on a keypad of an electronic device. The method includes the steps of generating light in the electronic device, and transmitting the light to the key through a light guide from a location in the light guide underlying the key to illuminate the key.